The average lifetime of smoke detectors that a company manufactures is 5 years, or 60 months, and the standard deviation is 8 months. find the probability that a random sample of 30 smoke detectors will have a mean lifetime between 58 and 63 months

0.8945

Step-by-step explanation:

Let x represents the lifetime of smoke detectors that a company manufactures.

We assume that the lifetime of smoke detectors that a company manufactures is normally distributed.

Given : The average lifetime of smoke detectors that a company manufactures is 5 years, or 60 months, and the standard deviation is 8 months.

i.e.

Sampl siez : n= 30

Then, the probability that a random sample of 30 smoke detectors will have a mean lifetime between 58 and 63 months will be :-

Hence, the probability that a random sample of 30 smoke detectors will have a mean lifetime between 58 and 63 months= 0.8945

1/4 because there is 4 grades.

step-by-step explanation:

y = | -2(-2) |     →     y = | 4 |     →     y = 4       ⇒   (-2, 4)

y = | -2(-1) |     →     y = | 2 |     →       y =   2       ⇒   (-1, 2)    

y = | -2(0) |     →     y = | 0 |     →       y = 0         ⇒   (0, 0)

y = | -2(1) |   c →     y = | -2 |     →     y =   2         ⇒   (1, 2)    

y = | -2(2) |     →     y = | - 4 |     →     y =   4         ⇒   (2, 4)